Habitat-Specific Foraging by Striped Bass (Morone saxatilis) in the San Francisco Estuary, California: Implications for Tidal Restoration

Non-native predatory fish strongly affect aquatic communities, and anthropogenic habitat
alterations can exacerbate their effects. Loss of natural habitat, and restoration actions that
reverse habitat loss, can modify relationships between non-native predators and prey.
Predicting how these relationships will change is often difficult because insufficient information
exists on the habitat-specific feeding ecology of non-native predators. To address this information
gap, we examined diets of non-native Striped Bass (Morone saxatilis; 63 to 671 mm standard length;
estimated age 1 to 5 yrs) in the San Francisco Estuary during spring and summer in three
habitat types—marsh, shoal, and channel—with the marsh habitat type serving as a model for
ongoing and future restoration. Based on a preyspecific index of relative importance, Striped Bass diets were dominated by macroinvertebrates in spring and summer (amphipods in spring, decapods and isopods in summer). In spring, diets were relatively consistent across habitats. In summer, marsh diets were dominated by sphaeromatid isopods and shoal/channel diets by idoteid amphipods and decapods. Striped Bass consumed a variety of native and non-native fishes, primarily Prickly Sculpin (Cottus asper) and Gobiidae. The highest importance of fish prey was in the marsh in spring (~ 40% prey weight), and fish prey comprised less than 25% prey weight in all other season/habitat combinations. Linear discriminant analyses suggested that marsh foraging was prevalent in Striped Bass collected in other habitats, mostly because of the predominance of marsh-associated invertebrates found in the stomachs of individual Striped Bass collected outside the marsh. Striped Bass diets differ across habitats, with marsh foraging important to Striped Bass regardless of collection location. This information can be used to forecast the potential utilization of restored habitats by this non-native piscivore.